Conventionally, there has been known a magnetic disk device provided with a magnetic head that performs thermally assisted magnetic recording by using near-field light with respect to a magnetic disk having high coercivity. In such a device, the magnetic head includes: a near-field light generating element that generates near-field light; and a magnetic pole for writing data to a magnetic disk. Upon writing data to the magnetic disk, such a device temporarily and locally heats up the magnetic disk by the near-field light generated by the near-field light generating element. Then, the device writes data with respect to a region of the magnetic disk at which coercivity is decreased by the heating. Consequently, the recording density of the magnetic disk is increased.
Recently, for such a magnetic disk device, it is desired to further improve writing quality with respect to the magnetic disk.